Difficulties frequently arise in achieving effective deposition of benefit agents onto hair or skin when the benefit agent is delivered by means of incorporation into rinse-off compositions, typically hair and body shampoos. Especially benefit agents which are water- and/or surfactant-soluble are often preferentially rinsed away from the intended site of deposition, rather than being deposited thereat and there have hitherto been numerous proposals in the art seeking to enhance deposition of such materials from these kinds of compositions.
This problem is particularly pronounced in the context of cleansing compositions, where the benefit agent to be deposited is surfactant-soluble, yet may still be water-insoluble. Hitherto there has been little, even no, study of deposition problems of specifically surfactant-soluble, often oily, benefit agents from this type of system.
There is much prior art relating to oil-based cleansing compositions such as in the form of creams, lotions, gels, milks or the like, e.g. comprising emulsions, which contain oily benefit agents such as sunscreens for deposition onto skin. As well as being intended primarily as a leave-on, rub-off-resistant and often water-resistant type of product, these compositions also contain no or little surfactant, so are unsuitable for cleansing purposes, either for the skin or for the hair.
Modification of these known compositions by simple addition of surfactant in order to give desirable detergency properties is not possible, because little deposition of the sunscreen or other benefit agent which is surfactant-soluble results, as a consequence of the agent being solubilized by the surfactant and easily carried away from the intended site of deposition as the composition is rinsed off.
US2015030557 (PROCTER AND GAMBLE CO) discloses consumer product compositions providing enhanced hydrophobic benefit agent deposition. The benefit agent is provided as a benefit agent/deposition aid emulsion, where the benefit agent is physically adsorbed to the deposition aid before the emulsion is added to the balance of ingredients. The emulsions and products facilitate increased deposition and retention of benefit agents contained therein onto a substrate.
WO/2005/068594 (UNILEVER PLC) discloses a cleansing composition capable of enhancing deposition of benefit agent comprising: i. a functional oil-in-water emulsion comprising 0.1% to 5% by weight benefit agent solubilised/dispersed in an oil and emulsified in water using a cationic emulsifier having an HLB greater than 8 such that the ratio of oil:cationic emulsifier is in the range 20:1 to 1:1; ii. a detergent active composition comprising 5% to 80% detergent active; and iii. a cationic polymer.
EP0552024 (Unilever) discloses rinse-off cleansing composition including one or more surfactant-soluble cosmetic agents for deposition onto hair or skin, the composition comprising a stable emulsion having a continuous phase comprising one or more surfactants and an internal phase comprising one or more oil materials, wherein the internal oil phase contains the said one or more surfactant-soluble cosmetic agents.
There therefore exists in the art a problem of poor availability and deposition of surfactant-soluble benefit agent from a rinse-off cleansing composition containing significant amounts of surfactant. Among other disadvantages, this leads to non-cost-effective use of and waste of (which may possibly be undesirable for environmental or health reasons) cleansing raw materials.